This invention relates to telemetry and, more particularly, to wireless transmission of data through a medium where radiowaves cannot be used.
Radiowaves are so sharply attenuated in rock formations due to their water content that the range of radio transmission through subterranean rock formations is very small, namely, in the order of several feet, or at most several yards. Wire transmission is also difficult in applications requiring data communication from a subterranean point, such as emergency communication in an underground mine or temperature telemetry in an in situ oil shale retort.